General
Sacland Tendrils (by Jin15) based brew to exploit scheming symmetry + lion's eye diamond + chromatic sphere/chromatic star with several wincons. The deck wins either with Doomsday + Thassa's Oracle or with creating lots of Aeve, Progenitor Ooze / Empty the Warrens or storming out with Tendrils of Agony.
Add some mana, play a sphere and play Scheming Symmetry to put the wincon (or protection/removal/additional mana) on top of your deck and draw into it by saccing a sphere. Scheming Symmetry is of course symmetric so OP can search for an answer, but because you have several different wincons it is difficult to guess the right answers and most of the time you win the same turn, so the answer OP finds doesn't matter.
1) Basic Doomsday-piles
Basic 2 mana pile, i.e. 2 mana left after Doomsday + a way to draw into the pile (f.i. a Chromatic Sphere in play):
Manamorphose (top)
Manamorphose
Manamorphose
Manamorphose
Thassa's Oracle (bottom)
Basic 1 mana pile (also needs 2 dummy cards in hand + loses to spot removal on Thassa's Oracle)
Brainstorm (top)
Lotus Petal
Lion's Eye Diamond
Ponder
Thassa's Oracle (bottom)
NOTE: Thought Scour (instead of Ponder) would make the pile resistant to removal (and also makes it easier to reach threshold or mill the card OP found with your Scheming Symmetry), but Ponder is still a generally better card to have in the deck (idem for Consider/Street Wraith/Deep Analysis).
2) Protection
Against counters: multiple threats (Burning Wish/Scheming Symmetry) and Silence + Pact of Negation. More protection in the sideboard. Surgical Extraction can be useful to see their hand (adds free storm count).
Against permanent hate: Prismatic Ending + Abrupt Decay from the sideboard. And the main deck Barbarian Rings can kill Thalia, Guardian of Thraben and Collector Ouphe. Still can be quite tough. EDIT: changed Prismatic Endings into extra Abrupt Decay and one Hurkyl's Recall
Against discard: the deck is fairly resistant to discard; you can play out the lands+artifacts and wait till you draw a business spell.
Against Wasteland: pray that you draw more lands than they draw Wasteland... (you could consider running Pithing Needle in the sideboard, but as you need to draw it, you might as well hope to draw a land).
Against reanimator: pray. There is Surgical Extraction + Tormod's Crypt from the board, but the matchup remains unfavorable. Although occasionally you encounter a careless reanimator player that recklessly uses Griselbrand activations + Thoughtseize to get as low as 2 life, and then you can snipe him with Barbarian Ring. It happens more often than you would think.
NOTE: Remember that Chromatic Star doens't draw a card when OP has a Leyline of the Void or Dauthi Voidwalker in play. Hence we only run 3 Chromatic Star and 4 Chromatic Sphere. Chromatic Sphere is also superior in that its draw effect is attached to its mana ability, so that the draw effect does not go to the stack. Hence, OP cannot respond to the draw (which is sometimes useful, f.i. when you have put something on top of your deck and OP has a Surgical Extraction in hand, or any other effect that makes you shuffle your library.